1. Field
Embodiments of the present invention may generally relate to optical communication systems. More particularly, embodiments of the present invention may relate to a colorless optical transceiver and an optical communication system including the same.
2. Background
In an optical wavelength division multiplexing (WDM) communication system, different wavelengths of light are transmitted and received through an optical fiber. Thus, a large amount of data can be transmitted at a time and a bandwidth can be increased. Further, the rental or management cost of an optical line can be reduced by using one optical fiber instead of a number of optical fibers.
In the conventional WDM, different wavelengths are outputted from optical transceivers for their respective channels. Further, the different wavelengths are inputted to a wavelength division multiplexer, which is configured with thin film optical filters or arrayed waveguide gratings. Thus, different optical transceivers are needed for the respective channels. Also, one or more spare optical transceivers should be prepared per channel for maintenance and repair purposes.
Korean Patent No. 10-0325687 entitled “A low-cost WDM source with incoherent light injected Fabry-Perot semiconductor laser diode” and U.S. Patent Publication No. 2003/0007207 entitled “Optical signal transmitter” disclose a colorless (or color free) wavelength division scheme. According to this scheme, the wavelength output from the optical transceiver is determined with a wavelength allocated to a port between the optical transceiver and the wavelength division multiplexer. Light output from an incoherence broadband light source (BLS) is guided to the thin film optical filters or the arrayed waveguide gratings and injected into a Fabry-Perot Laser Diode (FP-LD), a Semiconductor Optical Amplifier (SOA) or a Reflective Semiconductor Optical Amplifier (RSOA) (collectively referred to as FP-LD). The wavelength of output light from FP-LD is locked to that of an incoherent or coherent external injection light, thereby obtaining a specific wavelength.
In the conventional optical transceivers, the intensity of the external-injection light is not uniform. Further, the external-injection light and the light output from FD-LD itself may not be discriminated against each other. These problems cause errors in controlling FP-LD. Thus, it is difficult to obtain a stabilized output from the optical transceiver and to maintain uniform extinction ratio relating to the quality of optical signals.